The major objective of the proposed investigation is to elucidate the basic mechanisms by which triacylglycerols are absorbed from the intestine. The distribution of the enzymes involved in this process within the endoplasmic reticulum will be examined. The purification of the enzymes will be achieved by standard solubilization and fractionation procedures for membrane bound enzymes followed by affinity chromatography. The mechanism of induction of the enzymes involved in lipid absorption and regulation of these processes will be studied. The intestinal enzymes involved in cholesterol esterification in the intestinal mucosa will be purified, cofactor requirements established, and mechanisms of induction studied. Th monacylglycerol pathway will be quantitated in adipose tissue and the relationship and regulatory mechanism of this pathway to the glycerol-3-phosphate pathway investigated. The role of the former pathway in thermogenesis in brown adipose tissue will be studied. The lipid biosynthetic enzymes involved in fat absorption and lung maturation will be further studied in the developing rat and rabbit fetuses. The mechanism for the regulation of $ these processes will be studied. These include the mechanism of induction, the establishment of the rate limiting enzyme, etc. The substrate specificity of phosphatidic acid phosphohydrolase will be examined in various cells and tissues ranging from E. coli to mammalian subcellular fractions. The role of this and other closely related enzymes in the regulation of glycerophospholipid biosynthesis during evolution will be evaluated. The mechanism of plasmologen biosynthesis will be examined using specific antibodies to the various enzymes involved in the associated microsomal electron transport system. The explanation for the failure of yeast mitochondria to oxidize fatty acids will be examined.